Their safeties are the fact that you have to manually pull back the hammer to fire the weapon. Basically impossible to negligently discharge, barring a few that don’t have a strike plate between the firing pin and hammer, meaning a strong blow to the hammer can shoot off a chambered round.

Double action revolvers can also typically be operated as a single action, manually cocking the hammer. This also removes the other Xtra weight from the trigger, which was just the force added by having to cock the hammer and rotate the cylinder.